Installation for fighting fire

ABSTRACT

An installation for fighting fire, having a hydraulic accumulator which has at least one pressure container with a space for extinguishing liquid and a space for propellant gas, a rising tube arranged in the pressure container and provided with a side opening and, at the lower part of the pressure container, a feed opening for feeding extinguishing liquid into the rising tube and further to at least one nozzle. In order to obtain an extremely small drop size of the extinguishing liquid at the final stage of the emptying of the pressure container and in order to manage with a very small amount of extinguishing liquid, the rising tube has a throttle in an area below the uppermost side opening.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an installation for fighting fire,including a hydraulic accumulator which includes at least one pressurecontainer with a space for extinguishing liquid and a space forpropellant gas, a rising tube, in the pressure container, provided witha side opening and, at the lower part of the pressure container, with afeed opening for feeding extinguishing liquid into the rising tube andfurther to at least one nozzle.

2. The Prior Art

Such installations are known from, for example, WO 94/08659. Theprincipal of operation is that only liquid in a mist-like, penetratingform is initially sprayed from the nozzle, after which gas is mixed intothe liquid through said the openings. A reduction of the pressure in thepressure container generally produces a spray with a larger drop sizeout of the nozzle. Owing to the feeding of gas, the drop size of theextinguishing medium discharged from the nozzle can be reduced. Theseknown installations largely function very well; however, in someapplications, it would be desirable to be able to reduce the size of thedrops discharged from the nozzle even more, after the initial sprayingwith a great penetration, than what has been possible with the knownhydraulic accumulators and nozzles. The mixing of a large amount of gasinto a small amount of liquid has been relatively difficult to achievein practice. An enlarging of the side openings in the rising tube hasnot produced the desired result, but by reducing the diameter of therising tube, it has been possible to improve the intermixing of gassomewhat. However, a reduction of the diameter of the rising tubeincreases the pressure losses as the flow resistance of the liquid inthe rising tube increases, and sufficient liquid cannot be obtained fromthe pressure container upon emptying the container. By being able toproduce very small droplets, the amount of extinguishing liquid that isused could be minimized and, simultaneously, if water was used as theextinguishing liquid, the water damages would be minimal. This has notalways been possible to achieve to such a degree as one would havewished.

SUMMARY OF THE INVENTION

The present invention relates to a new installation for fighting fire bymeans of which a very finely divided mist, when a pressure accumulatoris used, can be easily produced at the final stage of the extinguishing,after the extinguishing with a mist-like liquid spray with a greatpenetrating ability and a relatively large drop size has initially beenstarted. The installation can, if desired, easily be realized by mixinggas into the extinguishing liquid already when the emptying of thepressure container is started.

To produce such an extinguishing medium with a very finely divided mistwith extremely small droplets, the invention is characterized in thatthe rising tube of the pressure container has a throttle in an areabelow the side opening.

By arranging the throttle below the lowermost side opening, gas can flowefficiently in through all the side openings, when the liquid level hassunk below the lowermost side opening. If the throttle was located abovethe lowermost side opening, only liquid could flow in through thelowermost side opening at the end of the emptying of the pressurecontainer.

By arranging side openings at at least three different height levels inthe rising tube, good results are achieved for many applications. Insome cases, it would be possible to arrange side openings only at twodifferent height levels or only one side opening.

Preferably, the pressure container is filled with water or a water-basedliquid, whereby a gas source which is filled with nitrogen and which hasa pressure in the range of about 60 to 200 bar is coupled to thepressure container. By using nitrogen, an extinguishing medium with verysmall droplets is obtained when nitrogen and water are intermixed. Theextinguishing medium weighs slightly more than air, wherefore it willsink to the lower part of a room in which it is sprayed. After sometime, the nitrogen is liberated from the water mist and rises in theroom. When the nitrogen rises, the oxygen content in the room decreases,and an extinguishing effect is thus achieved.

The essential idea of the invention is that a relatively large pressuredifference is achieved outside and inside the rising tube by means ofthe throttle. As a result of the pressure difference, gas is caused toflow efficiently through the side opening/side openings from the outsideof the rising tube into the rising tube, when the liquid level haspassed the level of the side opening/side openings, whereby an effectivemixing of gas into the liquid leaving the rising tube takes place. Suchan effective gas flow is not achieved in known constructions, since thepressure difference outside and inside the rising tube--contrary to whathas been assumed--is very small. In the known constructions, the gasflows in through the side openings--contrary to what has beenassumed--through the ejector effect as the extinguishing liquid, whichflows with a high velocity in the rising tube, produces a negativepressure at the side openings which pulls along gas.

The greatest advantage of the present invention is that a very effectivemixing of incombustible gas into a small amount of extinguishing liquidis achieved, whereby, by spraying through suitable nozzles, anextinguishing medium mist in the form of a mixture of liquid and gascontaining very small droplets is achieved, the drop size being fromabout 10 to 50 μm, which very efficiently extinguishes a fire when thefire has first been--as is normally the case--forced down by liquid mistwith a larger drop size of about 50 to 250 μm. It is also conceivablethat a constant small drop size of, for example, 10 to 50 μm may besustained during the entire extinguishing. Such an extinguishing mediummist can be sprayed so that it first fills the entire room, after whichit--depending on the composition of the incombustible gas--can--if themixture of liquid and gas is heavier than air--sink towards the floor,after which the gas component of the liquid and gas mixture, if it islighter than air, can after a period of time be liberated from theliquid and rise, whereas the liquid mist sinks down.

The invention shall be described in the following with reference to oneembodiment by means of the appended drawings

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows prior art,

FIG. 2 shows a detail of FIG. 1,

FIG. 3 shows the present invention, and

FIG. 4 shows a detail of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, which shows prior art, the reference numeral 1 indicates ahydraulic accumulator which consists of a pressure container 2 forliquid. A gas bottle 4 has been coupled to the pressure container 2through a conduit 3a with a valve 3b. The space 5 of the pressurecontainer 2 contains water, the volume of the space being typicallyabout 50 l. The gas bottle 4, which has a volume of about 50 l, containsnitrogen or some other incombustible gas. The pressure in the gas bottleis typically from 100 to 300 bar before an extinguishing process isinitiated. The advantage of using nitrogen is that a suitable weight forthe extinguishing medium is achieved so that the extinguishing mediumcan first settle against the floor and the gas component of theextinguishing medium can later rise, as it appears from the above.

The pressure container 2 comprises a gas feeding pipe 6 connected to theconduit 3a and a rising tube 7 which extends down from the pressurecontainer up to an outfeed pipe 8 which via a valve 9 leads to a numberof nozzles 10 to 12. The number of nozzles can of course vary. Therising tube 7 comprises a number of side openings 13 to 15 at a distancefrom one another and, at the lower end, a feed opening 16.

When an installation according to FIG. 1 is put into operation, thevalve 9 opens and the valve 3b is kept open. Nitrogen gas is then fedinto the upper part of the pressure container, i.e. the space 17, inwhich an initial pressure of, for example, 180 bar is formed. Thenitrogen functions as propellant gas for driving out water from thepressure container 2. The water flows as a result of the gas pressure inthrough the feed opening 16 of the rising tube 7 and somewhat throughthe side openings 13 to 15. On emptying the pressure space, the waterlevel 19 sinks, whereby the volume of the space 17 for gas increases.Initially, only water flows through the rising tube 7, until the waterlevel 19 has sunk to the place where the side opening 13 is located.Nitrogen gas then starts to be mixed into the water as nitrogen gasflows through the side opening 13. The gas pressure has fallen to avalue under 180 bar when the water level has sunk to the level of theside opening 13. When the emptying of the pressure container 2 proceeds,at the same time as the pressure in the pressure container falls, thewater level gradually reaches the level where the side opening 14 islocated. Nitrogen gas is then also fed in through the side opening 14.The emptying of the pressure container 2 continues until the sideopening 15 has been passed and the pressure space has been emptied ofwater.

When the pressure space 2 according to FIG. 1 is emptied in the abovedescribed manner, it is not possible to obtain extremely small droplets,e.g. from 10 to 20 μm, at the end of the emptying process. This is dueto the fact that the main driving force which causes gas to flow inthrough the side openings 13 to 15 is based on the ejector effect of thewater jet which flows in the rising tube 7. This ejector effect can beincreased when the diameter d1 (cf. FIG. 2, which shows a section of therising tube 7) is reduced: a reduced diameter d1 results in a fasterflow of the water, which in turn produces a stronger suction andejection effect. However, it has not been possible to use very smalldiameters d1, since in that case it would not be possible to obtain asufficiently great water flow per time unit. Since the pressure p1--inFIG. 2 outside the rising tube 7 is very near the pressure p2 inside therising tube, it has also not been possible to produce--by the pressuredifference p1-p2-a flow of nitrogen gas through the side opening 15.This has particularly been the case when only a small number of nozzlesthat are put into operation, e.g. only the nozzle 11, has been released.If a larger series of nozzles 10 to 12 has been released, it has beenpossible to achieve a small pressure difference p1-p2, but not apressure difference sufficiently large to make the intermixing of gasvery efficient, which would be vital in order to keep the drop size ofthe extinguishing medium very small.

FIG. 3 shows a simple embodiment of an installation according to thepresent invention. Reference marks corresponding to those of thecorresponding parts in FIG. 1 have been used.

The invention in FIG. 3 differs from the known construction in FIG. 1therein that the rising tube 7' at its lower part is throttled by athrottle 18'. The throttle 18' has been formed as a constriction made inthe lower end of the rising tube 7' below the lowermost side opening15'. The throttle 18' forms an aperture 18' with the diameter d2=0.5 mm,whereas the nominal diameter d1 of the rising tube 7' is typically inthe range of 8 to 15 mm. The aperture 18' preferably has the diameterd2=0.2 to 4 mm and most preferably 0.3 to 2mm. The selection of thediameter d2 for the aperture 18' depends on many factors, such as thetype of nozzles 10', 11', 12', the number of nozzles, the propellantpressure in the gas bottle 4', the type of gas, the diameter d1 of therising tube 7', the size and number of the side openings 13' to 15', theintended use of the installation, i.e. the type of fire to be fought.

As a result of the throttle 18', a greater pressure difference p1-p2 isformed, at the side openings 13', 14' and 15', outside and inside therising tube 7'. This pressure difference, which can, for example, be inthe order of 50 bar, causes nitrogen gas to flow efficiently in throughthe side openings 13' to 15' when the water level in the pressurecontainer 2' has sunk to a level below the side opening 13'. Due to thefact that gas can flow efficiently into the side openings as thepressure container 2' is emptied, it is possible to obtain, as a result,a drop size of the sprays discharged from the nozzles 10' to 12' that isvery small at the end of the extinguishing. The system functionssuccessively so that the proportion of gas/water is determined by thelocation of the water level 19' in the pressure bottle 2'. At first, theside openings 13' to 15' and the feed opening 16' provide only waterthrough the throttle 18' into the rising tube 7'. When the water level19' has reached the side opening 13', the side opening 13' starts tofeed gas into the rising tube 7', while the rest of the side openings14', 15' and the feed opening 16' provide water through the throttle18'. At this water level, the pressure is still comparatively high,whereby the amount of gas which is required to obtain small droplets iscomparatively small. The drop size increases with the falling pressureif the rest of the parameters are kept unchanged. Consequently, when thepressure falls, more gas is successively required to obtain smalldroplets. When the water level has sunk to the side opening 14', theamount of gas increases and the amount of water is reduced. This is dueto the fact that both side openings 13' and 14' provide gas, whereasonly the side opening 15' and the feed opening 16' provide water throughthe throttle 18'. When the water level has reached a level below theside opening 15', the amount of gas that is intermixed is very large inrelation to the amount of water, which only flows from the feed opening16' through the throttle 18'.

The spray heads and/or the sprinklers in which the nozzles have beenmounted are preferably of the type described in the publications WO92/20453, WO 92/22353 and WO 94/16771.

If the throttle 18' is formed by an aperture with a diameter d2 that issmall in relation to the diameters of the side openings 13' to 15', thepressure difference p1-p2 grows very large and liquid can flow inthrough the side openings. The diameter of the side openings ispreferably between 0.5 and 5 mm and most preferably between 1 and 3 mm.In the embodiment in FIG. 3, the rising tube 7' has a side opening 13'with a diameter of 2 mm in the upper part, two side openings 15' with adiameter of 2 mm in the lower part and, about half-way between said sideopenings 13' and 15', a side opening 14' with a diameter of 2 mm so thatthe pressure container 2' is divided into four sections I to IV ofapproximately the same size. As there are three side openings 13' to 15'located at a distance from one another, the lowermost side opening 15'being located in the lower part of the rising tube 7' and the uppermostside opening 13' being located in the upper portion of the rising tube,an efficient mixing of gas into the water is achieved for a long periodof time during the emptying of the pressure container 2'. By making thelowermost opening 15' larger than the rest of the side openings, anextremely efficient intermixing of gas is achieved towards the end ofthe emptying of the pressure container 2'. Since the intermixing of gasis efficient, a small amount of water will suffice. In FIG. 3, thevolume of the pressure container 2' is only 5 l compared to 50 l in FIG.1.

In FIG. 3, the throttle 18' has been arranged below the lowermost sideopening 15', whereby a large pressure difference is achieved at all theside openings 13' to 15', which is advantageous in the attempt to mix aslarge a quantity of gas as possible into the water. It is, however,conceivable that the throttle 18' may be arranged at a different place,e.g. between the side openings 13' and 14', whereby a larger pressuredifference is achieved only at the side opening 13'. It is important forthe invention that the throttle 18' has been arranged below theuppermost side opening 13', whereby a greater pressure difference isachieved at least at this side opening, causing gas to flow in throughthe side opening when the water level has sunk to the height level ofthis side opening.

The water in the pressure container 2 may or may not contain additives.

Instead of nitrogen, the gas bottle 4' may contain some otherincombustible gas, such as argon or carbon dioxide. Incombustible gaswhich weighs less than air is to be preferred, if it is wished that thegas can later rise so that an extinguishing effect is achieved higher upin the room. Consequently, nitrogen may well be used.

The invention has in the foregoing been described with reference to onlyone embodiment and it is therefore pointed out that the invention canvary as regards its details in many ways within the scope of theenclosed claims. Thus the throttle can be constructed, for example, asan aperture which has been made in the pipe wall of the rising tube atthe lower end of the rising tube. The number of side openings in therising tube can be much larger than what has been shown in the figures.It is also conceivable that there may only one side opening, although atleast two side openings located at a distance from one another in thelongitudinal direction of the rising tube is to be preferred. The solefunction of the valve 9' is to stop the feed of liquid to the nozzles;the valve is thus not necessary for the invention.

I claim:
 1. Installation for fighting fire, comprising a hydraulic accumulator (1') which comprises at least one pressure container (2') defining a lower space (5') for extinguishing liquid and an upper space (17') for propellant gas, and a rising tube (7') positioned in the pressure container, said rising tube including a feed opening (16') for feeding extinguishing liquid into the rising tube and upwardly therein to at least one nozzle (10' to 12'), first and second vertically spaced apart side openings above the feed opening, and a throttle therein below at least one of said first and second side openings.
 2. Installation according to claim 1, including gas supply means connected to the pressure container (2') to provide the pressure container (2') with propellant gas.
 3. Installation according to claim 1, wherein the throttle is located below both of said first and second side openings.
 4. Installation according to claim 1, wherein the throttle is formed by a constriction in the rising tube (7'), whereby the constriction forms an aperture (18') with a diameter of 0.2 to 2 mm in the rising tube.
 5. Installation according to claim 4, wherein the aperture (18') has a diameter of 0.3 to 2 mm.
 6. Installation according to claim 1, wherein the rising tube (7') has three side openings (13' to 15') which have been placed at a distance from one another in the longitudinal direction of the rising tube so that the lower space (5') for extinguishing liquid of the pressure container (2') in the area between said side openings is divided into sections (II, III) lacking side openings.
 7. Installation according to claim 6, wherein the distances between the three side openings (13' to 15') are essentially of the same length.
 8. Installation according to claim 6, wherein the diameter of the side openings (13' to 15') is 0.5 to 5 mm.
 9. Installation according to claim 8, wherein the diameter of the side openings (13' to 15') is 1 to 3 mm.
 10. Installation according to claim 9, wherein rising tube (7') has, at the lower part, at a distance from the feed opening (16') of the rising tube, at least one side opening (15') the diameter of which is larger than the diameter of side openings (13', 14') located higher up in the rising tube.
 11. Installation according to claim 2, wherein the gas supply means is a pressure bottle (4') contains incombustible gas.
 12. Installation according to claim 11, wherein the pressure bottle contains nitrogen charged to a pressure of from 30 to 300 bar.
 13. Apparatus for fighting fire comprising:a pressure container which defines a lower space for containing extinguishing liquid and an upper space for propellant gas, a pressure bottle containing incombustible gas connected to said pressure container, and a rising tube positioned in the pressure container, said rising tube including a feed opening (16') for feeding extinguishing liquid into the rising tube and upwardly therein to at least one nozzle (10' to 12'), first and second vertically spaced apart side openings above the feed opening, and a throttle therein below at least one of said first and second side openings.
 14. Apparatus according to claim 13, wherein said throttle is located below both of said first and second side openings.
 15. Apparatus according to claim 13, including a third side opening vertically spaced from said first and second side openings.
 16. Apparatus according to claim 13, wherein said throttle is located below all of said first, second and third side openings.
 17. Apparatus according to claim 13, wherein said throttle is formed by a construction in said rising tube.
 18. Apparatus according to claim 12, wherein said rising tube has an internal diameter of between 8 and 15 mm and said constriction has a diameter of between 0.2 and 4 mm.
 19. Apparatus according to claim 18, wherein said constriction has a diameter of between 0.3 and 2 mm. 